1. Field of the Invention
The present invention relates to a phase adjusting device and a phase adjusting method for performing phase (timing) adjustment of a pulse used for imaging in the digital camera, as well as a digital camera incorporating the phase adjusting device.
2. Description of the Related Art
In digital cameras (a digital still camera, a digital video camera, a mobile phone with a built-in camera, and the like), an analog imaged signal that is imaged by an imaging element such as a CCD and an MOS sensor is converted to a digital imaged signal, and such digital imaged signal is subjected to a predetermined signal process and then recorded. The pulse for driving the imaging element, the pulse for detecting the signal level, and the like are required to image the subject with the imaging element. Since the phase of such pulses has variations originating from manufacturing, it is difficult to adjust the pulse phase when designing hardware. Thus, the technicians perform phase adjustment after manufacturing, store information indicating the adjusted phase in the storage region, and thereafter, read out the phase information from the storage region in actual use to set the optimum phase.
As disclosed in Japanese Laid-Open Patent Publication No. 2005-151081, a technique of mainly fetching noise component with the exposure time at a minimum and adjusting the phase under the condition the high frequency component (noise component) becomes minimum is conventionally known. This prior art example is hereinafter referred to as prior art example 1.
When environmental temperature fluctuates, the sample timing fluctuates due to temperature characteristics. In this case, noise occurs and the image quality degrades if the phase of the pulse remains fixed. The phase of the pulse thus must be adjusted, but rapid and easy response is difficult if the technician readjusts the phase by hand. Although the pulse to be adjusted exists in a plurality of types, the optimum phase is obtained in the prior art example 1 with the same method for all the pulses without taking characteristics of each pulse into consideration, and thus the precision is not very high.